A blood test doesn't help in diagnosing osteoarthritis, but it helps in diagnosing other types of arthritis or inflammatory conditions. For example, the people with rheumatoid arthritis show a higher level of antibodies that bind to citrulline-modified proteins, states WebMD.
Tests for inflammation are determined by the erythrocyte sedimentation rate, or ESR, and C-reactive protein, or CRP. Both CRP and ESR levels reveal disease activity and a person's response to treatment. A series of tests called the antinuclear antibody profile measure the abnormal antibodies levels that correspond to such diseases as Sjogren's syndrome, lupus, polymyositis and scleroderma, explains WebMD.
The presence of cryoglobulin antibodies in blood testing reveals diseases such as lupus, Sjogren's syndrome, Waldenstrom's macroglobulinemia, hepatitis B and C, rheumatoid arthritis and other infections, according to WebMD.